How an AI picks the next word

A chatbot doesn't plan a sentence and type it out. It does one tiny thing, over and over: guess the next word, then guess again with that word added.

Every guess is really a ranked list of options, each with a probability. Below is that list. Tap a word to add it — and watch a brand-new list appear for whatever comes next.

MODEL'S NEXT-WORD GUESSES

Tap any word to choose it.

That's the whole trick. There's no script and no lookahead — just a probability for what plausibly comes next, sampled one word at a time. String thousands of those guesses together and you get an essay. Pick a less-likely option now and then, and you get a sentence that feels creative rather than robotic.

At each step, what is the model actually choosing?

The real models rank from a vocabulary of tens of thousands of word-pieces, not five — but the loop is exactly this. Want to know why temperature makes it more "creative," or what a token really is? Ask me in the chat.

Primary source · 3Blue1Brown — Transformers & how LLMs predict the next word